Grand Theft Auto V: No Happy Endings

Grand Theft Auto V has been praised for many things, mainly it's strange yet completely new three playable character system. Yet its most understated component is by far it's musical score. Grand Theft Auto V was the first game to have it's own ambient soundtrack as well, making it much more special for it. Unlike many games on this list, the music is portrayed in such a way that it weaved in and out of the missions, complimenting the action. I personally think that it deserves a lot more attention. No Happy Endings came into my head a few times and the 80's esque synthesizers give it a really nice retro feel.
No Happy Endings: http://www.youtube.com/watch?v=ArA3bkumvoI
Full OST can be found here. The music is split into three volumes. Original Music, The Score and The Soundtrack.
Original Music: http://www.youtube.com/watch?v=38t3deGsQk4
The Score: http://www.youtube.com/watch?v=5W6un86yPFA
The Soundtrack: http://www.youtube.com/watch?v=0uiB6a9yH1Y

Farcry 3 - Main Theme

The main surprise of 2012 by far. A somewhat lackluster story supported by phenomenal...everything else. The tropical island setting has been done many times, but not usually with grungy electronic backing tracks. It could be to contrast the difference between Vaas and Citra, who knows. All I know is, is that the soundtrack is fantastic.
Main Theme: http://www.youtube.com/watch?v=KAmN270P_Fg
Far Cry 3 OST: http://www.youtube.com/watch?v=XLk1CXgLO7s

Deus Ex: Human Revolution - Icarus

A bit like Grand Theft Auto V, the score to Deus Ex: Human Revolution was incredibly understated. The pulsing cyber-punk tones could be heard around every corner in Hengsha. The story of Icarus from Wikipedia, "Daedalus fashioned two pairs of wings out of wax and feathers for himself and his son. Daedalus tried his wings first, but before taking off from the island, warned his son not to fly too close to the sun, nor too close to the sea, but to follow his path of flight. Overcome by the giddiness that flying lent him, Icarus soared through the sky curiously, but in the process he came too close to the sun, which melted the wax. Icarus kept flapping his wings but soon realized that he had no feathers left and that he was only flapping his bare arms, and so Icarus fell into the sea in the area which today bears his name, the Icarian Sea near Icaria, an island southwest of Samos." Incredibly poignant when considering the events of the game.
Icarus: http://www.youtube.com/watch?v=RRmqSy-O3EY
Full OST: http://www.youtube.com/watch?v=NVqDxdYYLAk&list=PL4E1AE167C56AA012